"In 2007, the fourth major assessment of technical information on climate change by the Intergovernmental Panel on Climate Change (IPCC) was published in November. The year also saw continued release of new scientific findings on various aspects of climate change. The IPCC 'Fourth Assessment Report' (AR4) critically reviewed the research on science, impacts, and mitigation strategies, and underscored large areas of agreement on climate issues (as well as some important uncertainties and disagreements). The IPCC concluded that the Earth's climate unequivocally has warmed over the past century, and that while natural factors, including changes in solar irradiance and volcanoes, have played roles in the observed changes, 'most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.' Additional research published in 2007 showed continuously rising concentrations of greenhouse gases and temperatures, record loss of Arctic sea ice in the summer, transit by sailboat through the legendary Northwest Passage through the Arctic, and other markers of climate change. Additional research indicated several ecological risks -- including mortality of the eastern Pacific gray whale and lower survival rates among young polar bears -- linked to climate change. […] This report summarizes highlights of new scientific research and assessments released in 2007 related to global warming."
CRS Report for Congress, RL34266